/*
 * @(#)NameConstraintsExtension.java	1.22 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program is free software; you can redistribute it and/or  
 * modify it under the terms of the GNU General Public License version  
 * 2 only, as published by the Free Software Foundation.   
 *   
 * This program is distributed in the hope that it will be useful, but  
 * WITHOUT ANY WARRANTY; without even the implied warranty of  
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU  
 * General Public License version 2 for more details (a copy is  
 * included at /legal/license.txt).   
 *   
 * You should have received a copy of the GNU General Public License  
 * version 2 along with this work; if not, write to the Free Software  
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  
 * 02110-1301 USA   
 *   
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

package sun.security.x509;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.reflect.Array;
import java.security.Principal;
import java.security.cert.CertificateEncodingException;
import java.security.cert.CertificateException;
import java.security.cert.CertificateParsingException;
import java.security.cert.X509Certificate;
import java.util.*;

import javax.security.auth.x500.X500Principal;

import sun.security.util.*;
import sun.security.pkcs.PKCS9Attribute;

/**
 * This class defines the Name Constraints Extension.
 * <p>
 * The name constraints extension provides permitted and excluded
 * subtrees that place restrictions on names that may be included within
 * a certificate issued by a given CA.  Restrictions may apply to the
 * subject distinguished name or subject alternative names.  Any name
 * matching a restriction in the excluded subtrees field is invalid
 * regardless of information appearing in the permitted subtrees.
 * <p>
 * The ASN.1 syntax for this is:
 * <pre>
 * NameConstraints ::= SEQUENCE {
 *    permittedSubtrees [0]  GeneralSubtrees OPTIONAL,
 *    excludedSubtrees  [1]  GeneralSubtrees OPTIONAL
 * }
 * GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
 * </pre>
 *
 * @author Amit Kapoor
 * @author Hemma Prafullchandra
 * @version 1.15
 * @see Extension
 * @see CertAttrSet
 */
public class NameConstraintsExtension extends Extension
implements CertAttrSet {
    /**
     * Identifier for this attribute, to be used with the
     * get, set, delete methods of Certificate, x509 type.
     */
    public static final String IDENT = "x509.info.extensions.NameConstraints";
    /**
     * Attribute names.
     */
    public static final String NAME = "NameConstraints";
    public static final String PERMITTED_SUBTREES = "permitted_subtrees";
    public static final String EXCLUDED_SUBTREES = "excluded_subtrees";

    // Private data members
    private static final byte TAG_PERMITTED = 0;
    private static final byte TAG_EXCLUDED = 1;

    private GeneralSubtrees	permitted = null;
    private GeneralSubtrees	excluded = null;

    private boolean hasMin;
    private boolean hasMax;
    private boolean minMaxValid = false;

    // Recalculate hasMin and hasMax flags.
    private void calcMinMax() throws IOException {
        hasMin = false;
        hasMax = false;
        if (excluded != null) {
            for (int i = 0; i < excluded.size(); i++) {
                GeneralSubtree subtree = excluded.get(i);
                if (subtree.getMinimum() != 0)
                    hasMin = true;
                if (subtree.getMaximum() != -1)
                    hasMax = true;
            }
        }

        if (permitted != null) {
            for (int i = 0; i < permitted.size(); i++) {
                GeneralSubtree subtree = permitted.get(i);
                if (subtree.getMinimum() != 0)
                    hasMin = true;
                if (subtree.getMaximum() != -1)
                    hasMax = true;
            }
        }
        minMaxValid = true;
    }

    // Encode this extension value.
    private void encodeThis() throws IOException {
	minMaxValid = false;
        if (permitted == null && excluded == null) {
            this.extensionValue = null;
            return;
        }
        DerOutputStream seq = new DerOutputStream();

        DerOutputStream tagged = new DerOutputStream();
        if (permitted != null) {
            DerOutputStream tmp = new DerOutputStream();
            permitted.encode(tmp);
            tagged.writeImplicit(DerValue.createTag(DerValue.TAG_CONTEXT,
                                 true, TAG_PERMITTED), tmp);
        }
        if (excluded != null) {
            DerOutputStream tmp = new DerOutputStream();
            excluded.encode(tmp);
            tagged.writeImplicit(DerValue.createTag(DerValue.TAG_CONTEXT,
                                 true, TAG_EXCLUDED), tmp);
        }
        seq.write(DerValue.tag_Sequence, tagged);
        this.extensionValue = seq.toByteArray();
    }

    /**
     * The default constructor for this class. Both parameters
     * are optional and can be set to null.  The extension criticality
     * is set to true.
     *
     * @param permitted the permitted GeneralSubtrees (null for optional).
     * @param excluded the excluded GeneralSubtrees (null for optional).
     */
    public NameConstraintsExtension(GeneralSubtrees permitted,
                                    GeneralSubtrees excluded)
    throws IOException {
        this.permitted = permitted;
        this.excluded = excluded;

        this.extensionId = PKIXExtensions.NameConstraints_Id;
        this.critical = true;
        encodeThis();
    }

    /**
     * Create the extension from the passed DER encoded value.
     *
     * @param critical true if the extension is to be treated as critical.
     * @param value Array of DER encoded bytes of the actual value.
     * @exception IOException on error.
     */
    public NameConstraintsExtension(Boolean critical, Object value)
    throws IOException {
        this.extensionId = PKIXExtensions.NameConstraints_Id;
        this.critical = critical.booleanValue();

        if (!(value instanceof byte[]))
            throw new IOException("Illegal argument type");

        int len = Array.getLength(value);
	byte[] extValue = new byte[len];
        System.arraycopy(value, 0, extValue, 0, len);

        this.extensionValue = extValue;
        DerValue val = new DerValue(extValue);
        if (val.tag != DerValue.tag_Sequence) {
            throw new IOException("Invalid encoding for" +
                                  " NameConstraintsExtension.");
        }

        // NB. this is always encoded with the IMPLICIT tag
        // The checks only make sense if we assume implicit tagging,
        // with explicit tagging the form is always constructed.
	// Note that all the fields in NameConstraints are defined as
        // being OPTIONAL, i.e., there could be an empty SEQUENCE, resulting
        // in val.data being null.
	if (val.data == null)
	    return;
        while (val.data.available() != 0) {
            DerValue opt = val.data.getDerValue();

            if (opt.isContextSpecific(TAG_PERMITTED) && opt.isConstructed()) {
	        if (permitted != null) {
	            throw new IOException("Duplicate permitted " +
                         "GeneralSubtrees in NameConstraintsExtension.");
	        }
                opt.resetTag(DerValue.tag_Sequence);
	        permitted = new GeneralSubtrees(opt);

            } else if (opt.isContextSpecific(TAG_EXCLUDED) &&
                       opt.isConstructed()) {
	        if (excluded != null) {
	            throw new IOException("Duplicate excluded " +
                             "GeneralSubtrees in NameConstraintsExtension.");
	        }
                opt.resetTag(DerValue.tag_Sequence);
	        excluded = new GeneralSubtrees(opt);
            } else
	        throw new IOException("Invalid encoding of " +
                                      "NameConstraintsExtension.");
        }
	minMaxValid = false;
    }

    /**
     * Return the printable string.
     */
    public String toString() {
        return (super.toString() + "NameConstraints: [" +
                ((permitted == null) ? "" :
                     ("\n    Permitted:" + permitted.toString())) +
                ((excluded == null) ? "" :
                     ("\n    Excluded:" + excluded.toString()))
                + "   ]\n");
    }

    /**
     * Decode the extension from the InputStream.
     *
     * @param in the InputStream to unmarshal the contents from.
     * @exception IOException on decoding or validity errors.
     */
    public void decode(InputStream in) throws IOException {
        throw new IOException("Method not to be called directly.");
    }

    /**
     * Write the extension to the OutputStream.
     *
     * @param out the OutputStream to write the extension to.
     * @exception IOException on encoding errors.
     */
    public void encode(OutputStream out) throws IOException {
        DerOutputStream tmp = new DerOutputStream();
        if (this.extensionValue == null) {
            this.extensionId = PKIXExtensions.NameConstraints_Id;
            this.critical = true;
            encodeThis();
        }
        super.encode(tmp);
	out.write(tmp.toByteArray());
    }

    /**
     * Set the attribute value.
     */
    public void set(String name, Object obj) throws IOException {
	if (name.equalsIgnoreCase(PERMITTED_SUBTREES)) {
	    if (!(obj instanceof GeneralSubtrees)) {
		throw new IOException("Attribute value should be"
                                    + " of type GeneralSubtrees.");
	    }
	    permitted = (GeneralSubtrees)obj;
	} else if (name.equalsIgnoreCase(EXCLUDED_SUBTREES)) {
	    if (!(obj instanceof GeneralSubtrees)) {
		throw new IOException("Attribute value should be "
                                    + "of type GeneralSubtrees.");
	    }
	    excluded = (GeneralSubtrees)obj;
	} else {
	  throw new IOException("Attribute name not recognized by " +
			"CertAttrSet:NameConstraintsExtension.");
	}
        encodeThis();
    }

    /**
     * Get the attribute value.
     */
    public Object get(String name) throws IOException {
	if (name.equalsIgnoreCase(PERMITTED_SUBTREES)) {
	    return (permitted);
	} else if (name.equalsIgnoreCase(EXCLUDED_SUBTREES)) {
	    return (excluded);
	} else {
	  throw new IOException("Attribute name not recognized by " +
			"CertAttrSet:NameConstraintsExtension.");
	}
    }

    /**
     * Delete the attribute value.
     */
    public void delete(String name) throws IOException {
	if (name.equalsIgnoreCase(PERMITTED_SUBTREES)) {
	    permitted = null;
	} else if (name.equalsIgnoreCase(EXCLUDED_SUBTREES)) {
	    excluded = null;
	} else {
	  throw new IOException("Attribute name not recognized by " +
			"CertAttrSet:NameConstraintsExtension.");
	}
        encodeThis();
    }

    /**
     * Return an enumeration of names of attributes existing within this
     * attribute.
     */
    public Enumeration getElements() {
        AttributeNameEnumeration elements = new AttributeNameEnumeration();
        elements.addElement(PERMITTED_SUBTREES);
        elements.addElement(EXCLUDED_SUBTREES);

	return (elements.elements());
    }

    /**
     * Return the name of this attribute.
     */
    public String getName() {
        return (NAME);
    }

    /**
     * Merge additional name constraints with existing ones.
     * This function is used in certification path processing
     * to accumulate name constraints from successive certificates
     * in the path.  Note that NameConstraints can never be
     * expanded by a merge, just remain constant or become more
     * limiting.
     * <p>
     * IETF RFC2459 specifies the processing of Name Constraints as
     * follows:
     * <p>
     * (j)  If permittedSubtrees is present in the certificate, set the
     * constrained subtrees state variable to the intersection of its
     * previous value and the value indicated in the extension field.
     * <p>
     * (k)  If excludedSubtrees is present in the certificate, set the
     * excluded subtrees state variable to the union of its previous
     * value and the value indicated in the extension field.
     * <p>
     * @param newConstraints additional NameConstraints to be applied
     * @throws IOException on error
     */
    public void merge(NameConstraintsExtension newConstraints) 
	    throws IOException {

	if (newConstraints == null) {
	    // absence of any explicit constraints implies unconstrained
	    return;
	}

	/*
	 * If excludedSubtrees is present in the certificate, set the
	 * excluded subtrees state variable to the union of its previous
	 * value and the value indicated in the extension field.
	 */

	GeneralSubtrees newExcluded =
			(GeneralSubtrees)newConstraints.get(EXCLUDED_SUBTREES);
	if (excluded == null) {
	    excluded = (newExcluded != null) ?
			(GeneralSubtrees)newExcluded.clone() : null;
	} else {
	    if (newExcluded != null) {
		// Merge new excluded with current excluded (union)
		excluded.union(newExcluded);
	    }
	}

	/*
	 * If permittedSubtrees is present in the certificate, set the
	 * constrained subtrees state variable to the intersection of its
	 * previous value and the value indicated in the extension field.
	 */

	GeneralSubtrees newPermitted =
		(GeneralSubtrees)newConstraints.get(PERMITTED_SUBTREES);
	if (permitted == null) {
	    permitted = (newPermitted != null) ?
			(GeneralSubtrees)newPermitted.clone() : null;
	} else {
	    if (newPermitted != null) {
		// Merge new permitted with current permitted (intersection)
		newExcluded = permitted.intersect(newPermitted);

		// Merge new excluded subtrees to current excluded (union)
		if (newExcluded != null) {
		    if (excluded != null) {
			excluded.union(newExcluded);
		    } else {
			excluded = (GeneralSubtrees)newExcluded.clone();
		    }
		}
	    }
	}

	// Optional optimization: remove permitted subtrees that are excluded.
	// This is not necessary for algorithm correctness, but it makes 
        // subsequent operations on the NameConstraints faster and require 
        // less space.
	if (permitted != null) {
	    permitted.reduce(excluded);
	}

	// The NameConstraints have been changed, so re-encode them.  Methods in
	// this class assume that the encodings have already been done.
	encodeThis();

    }

    /**
     * check whether a certificate conforms to these NameConstraints.
     * This involves verifying that the subject name and subjectAltName
     * extension (critical or noncritical) is consistent with the permitted
     * subtrees state variables.  Also verify that the subject name and
     * subjectAltName extension (critical or noncritical) is consistent with
     * the excluded subtrees state variables.
     *
     * @param cert X509Certificate to be verified
     * @returns true if certificate verifies successfully
     * @throws IOException on error
     */
    public boolean verify(X509Certificate cert) throws IOException {

	if (cert == null) {
	    throw new IOException("Certificate is null");
	}

        // Calculate hasMin and hasMax booleans (if necessary)
        if (!minMaxValid) {
            calcMinMax();
	}

        if (hasMin) {
            throw new IOException("Non-zero minimum BaseDistance in"
                                + " name constraints not supported");
        }

        if (hasMax) {
            throw new IOException("Maximum BaseDistance in"
                                + " name constraints not supported");
        }

	X500Principal subjectPrincipal = cert.getSubjectX500Principal();
	X500Name subject = X500Name.asX500Name(subjectPrincipal);
	
	if (subject.isEmpty() == false) {
	    if (verify(subject) == false) {
		return false;
	    }
	}

	GeneralNames altNames = null;
	// extract altNames
	try {
	    // extract extensions, if any, from certInfo
	    // following returns null if certificate contains no extensions
	    X509CertImpl certImpl = X509CertImpl.toImpl(cert);
	    SubjectAlternativeNameExtension altNameExt = 
	    	certImpl.getSubjectAlternativeNameExtension();
	    if (altNameExt != null) {
		// extract altNames from extension; this call does not 
		// return an IOException on null altnames
		altNames = (GeneralNames)
			    (altNameExt.get(altNameExt.SUBJECT_NAME));
	    }
	} catch (CertificateException ce) {
	    throw new IOException("Unable to extract extensions from " +
			"certificate: " + ce.getMessage());
	}

	// If there are no subjectAlternativeNames, perform the special-case
	// check where if the subjectName contains any EMAILADDRESS
	// attributes, they must be checked against RFC822 constraints.
	// If that passes, we're fine.
	if (altNames == null) {
	    return verifyRFC822SpecialCase(subject);
	}
	
	// verify each subjectAltName
	for (int i = 0; i < altNames.size(); i++) {
	    GeneralNameInterface altGNI = altNames.get(i).getName();
	    if (!verify(altGNI)) {
		return false;
	    }
	}

	// All tests passed.
	return true;
    }

    /**
     * check whether a name conforms to these NameConstraints.
     * This involves verifying that the name is consistent with the
     * permitted and excluded subtrees variables.
     *
     * @param name GeneralNameInterface name to be verified
     * @returns true if certificate verifies successfully
     * @throws IOException on error
     */
    public boolean verify(GeneralNameInterface name) throws IOException {
	if (name == null) {
	    throw new IOException("name is null");
	}

	// Verify that the name is consistent with the excluded subtrees
	if (excluded != null && excluded.size() > 0) {
	
	    for (int i = 0; i < excluded.size(); i++) {
		GeneralSubtree gs = (GeneralSubtree)(excluded.get(i));
		if (gs == null)
		    continue;
		GeneralName gn = gs.getName();
		if (gn == null)
		    continue;
		GeneralNameInterface exName = gn.getName();
		if (exName == null)
		    continue;

		// if name matches or narrows any excluded subtree,
		// return false
		switch (exName.constrains(name)) {
		case GeneralNameInterface.NAME_DIFF_TYPE:
		case GeneralNameInterface.NAME_WIDENS: // name widens excluded
		case GeneralNameInterface.NAME_SAME_TYPE:
		    break;
		case GeneralNameInterface.NAME_MATCH:
		case GeneralNameInterface.NAME_NARROWS: // subject name excluded
		    return false;
		}
	    }
	}

	// Verify that the name is consistent with the permitted subtrees
	if (permitted != null && permitted.size() > 0) {

	    boolean sameType = false;

	    for (int i = 0; i < permitted.size(); i++) {
		GeneralSubtree gs = (GeneralSubtree)(permitted.get(i));
		if (gs == null)
		    continue;
		GeneralName gn = gs.getName();
		if (gn == null)
		    continue;
		GeneralNameInterface perName = gn.getName();
		if (perName == null)
		    continue;

		// if Name matches any type in permitted,
		// and Name does not match or narrow some permitted subtree,
		// return false
		switch (perName.constrains(name)) {
		case GeneralNameInterface.NAME_DIFF_TYPE:
		    continue; // continue checking other permitted names
		case GeneralNameInterface.NAME_WIDENS: // name widens permitted
		case GeneralNameInterface.NAME_SAME_TYPE:
		    sameType = true;
		    continue; // continue to look for a match or narrow
		case GeneralNameInterface.NAME_MATCH:
		case GeneralNameInterface.NAME_NARROWS:
		    // name narrows permitted
		    return true; // name is definitely OK, so break out of loop
		}
	    }
	    if (sameType) {
		return false;
	    }
	}
	return true;
    }

    /**
     * Perform the RFC 822 special case check. We have a certificate
     * that does not contain any subject alternative names. Check that
     * any EMAILADDRESS attributes in its subject name conform to these
     * NameConstraints.
     *
     * @param subject the certificate's subject name
     * @returns true if certificate verifies successfully
     * @throws IOException on error
     */
    public boolean verifyRFC822SpecialCase(X500Name subject) throws IOException {
	for (Iterator t = subject.allAvas().iterator(); t.hasNext(); ) {
	    AVA ava = (AVA)t.next();
            ObjectIdentifier attrOID = ava.getObjectIdentifier();
            if (attrOID.equals(PKCS9Attribute.EMAIL_ADDRESS_OID)) {
                String attrValue = ava.getValueString();
                if (attrValue != null) {
                    RFC822Name emailName;
                    try {
                        emailName = new RFC822Name(attrValue);
                    } catch (IOException ioe) {
                        continue;
                    }
                    if (!verify(emailName)) {
                        return(false);
		    }
                }
             }
        }
        return true;
    }
}
